1. Technical Field
The present disclosure relates to an onboard image display device for a vehicle, and particularly to an onboard image display device for a vehicle that displays an image by irradiating a window glass of a vehicle with image light.
2. Related Art
In recent years, onboard image display devices for a vehicle, so-called head-up displays (HUD) have been widely spread as a device to inform a driver of vehicle-related information such as a vehicle speed and navigation information (see, for example, Japanese Unexamined Patent Application Publication (JP-A) No. 2010-167830). The head-up displays each includes a projector that projects image light of an image and a display unit that displays the image projected from the projector.
The projector includes, for example, a light source, a transmissive liquid crystal panel that allow outgoing light from the light source to be entered and transmitted, a plane mirror that causes image light to be reflected, the image light being transmitted through the transmissive liquid crystal panel, and a concave mirror that divergently reflects the image light which has been reflected by the plane mirror. Each of devices is housed in a housing. It is to be noted that information displayed on the above-mentioned liquid crystal panel is reflected and enlarged to be displayed.
The display unit is, for example, a windshield glass and configured to receive image light from the projector for image formation and to display various types of information. Normally, the projector of a head-up display is provided within an instrument panel and image light from the projector is projected and displayed on the windshield glass on the driver side.
Japanese Unexamined Patent Application Publication (JP-A) No. 2006-205955 discloses a head-up display in which the projector is a stand-alone projector. In the implementation in JP-A No. 2006-205955, the projector is placed on an instrument panel, and image light from the projector is projected and displayed on the windshield glass on the driver side.
In the head-up display disclosed in JP-A No. 2010-167830, a projector is installed within an instrument panel, particularly on the rear-surface side of a meter, and a display unit is installed on the driver side of the windshield glass. Normally, in the instrument panel, instruments such as a speedometer, a tachometer, a fuel gauge, a water temperature gauge, and an odometer are disposed, the instruments indicating information necessary for driving a vehicle. In addition, a device such as an air duct is also disposed so that the instrument panel has no wasted space therein. Since the projector is to be installed within the instrument panel having such conditions, the capacity within the instrument panel needs to be increased in order to install the projector. Therefore, the capacity of the instrument panel has been increased to install the projector, and the space within the vehicle has been reduced accordingly. Also, the stand-alone projector disclosed in JP-A No. 2006-205955 is installed with its main body exposed, thereby causing a problem that the projector may present an obstacle and stability of irradiation and display of image light reduces due to a contact or the like.